Types of mixing and heterogeneities in siliciclastic-carbonate sediments

Abstract

Mixed siliciclastic-carbonate deposits consist of a suite of different types of mixing between the two components, from bed (core-plug) to stratigraphic (seismic) scales, producing a high vertical and lateral lithological variability. Mixed deposits result from the interaction of siliciclastic input and coeval carbonate production controlled by temporal and/or spatial factors. Although mixed deposits are very diffuse in the geological record, studies about these deposits are scrappy and not well encoded. Accordingly, mixed deposits represent a labyrinth for researchers who want to investigate them for the first time.In this paper, different types of mixing (compositional versus strata) controlled by different allocyclic (e.g. sea-level, climate) and/or autocyclic (e.g. depositional processes) factors that operate at different scale are documented. Mixing is recognized and described at three main scales of observation: bed/core-plug scale; lithofacies/well-log scale; and stratigraphic/seismic scale. (i) Compositional mixing reflects the contemporaneous accumulation of the two heterolithic fraction in space and time. This type of mixing is observable at lamina to bed scale, locally producing depositional structures diagnostic for particular depositional environments. (ii) Strata mixing results from the alternation of the two heterolithic fraction in time. This type of mixing is observable at lithofacies to stratigraphic scale and can be related to depositional processes, climatic variations and/or relative sea-level changes.A correct identification of these different types of mixing and the scale of their occurrence is crucial in revealing (i) physical processes that control the sedimentation, (ii) environmental factors that influence the carbonate factory related to the siliciclastic dispersal mechanisms, and (iii) internal heterogeneity of the resulting sedimentary deposit. Furthermore, the petroleum industry is interested to unravel new insights about internal properties of mixed siliciclastic-carbonate systems (e.g., porosity, permeability) and to reconstruct predictive 3D models for the related reservoirs. The correct prediction of internal heterogeneity and the recognition of lateral and vertical compartmentalization have an important impact on hydrocarbon exploration and exploitation.

Sedimentological Characteristics And Paleoenvironmental Implication Of Triassic Vertebrate Localities In Villány (Villány Hills, Southern Hungary)

“…The carbonate sediments of the dolomite lithofacies were deposited in a shallow, restricted lagoon environment, dolomarl (shallow marine sediments, where the enhanced terrigenous input was the results of the more humid climate), reddish silty claystone (paleosol) and sandstone (terrigenous provenance) indicating that the sediments of the Construction site were formed in inner ramp lagoon and related tidal flat environments. The alternation of siliciclast rich and carbonate rich sediments can be frequently interpreted as the results of short-term sealevel or climate changes (e.g., Wilson 1967;Brachert et al 2003;Colombié et al 2012;Caracciolo et al 2013;Zeller et al 2015;Blanchard et al 2016;Reis & Suss 2016;Chiarella et al 2017). The short-term sea-level changes have a significant control on the sedimentation of the shallow marine environment, because during the lowstands, carbonate sediment GEOLOGICA CARPATHICA, 2019, 70, 2, 135-152 production is slowed down or halted and the terrigenous influx can increase, resulting in the predominance of siliciclast deposition (Wilson 1967;Brachert et al 2003;Carcel et al 2010;Caracciolo et al 2013;Chiarella et al 2017 and references therein).…”

“…The alternation of siliciclast rich and carbonate rich sediments can be frequently interpreted as the results of short-term sealevel or climate changes (e.g., Wilson 1967;Brachert et al 2003;Colombié et al 2012;Caracciolo et al 2013;Zeller et al 2015;Blanchard et al 2016;Reis & Suss 2016;Chiarella et al 2017). The short-term sea-level changes have a significant control on the sedimentation of the shallow marine environment, because during the lowstands, carbonate sediment GEOLOGICA CARPATHICA, 2019, 70, 2, 135-152 production is slowed down or halted and the terrigenous influx can increase, resulting in the predominance of siliciclast deposition (Wilson 1967;Brachert et al 2003;Carcel et al 2010;Caracciolo et al 2013;Chiarella et al 2017 and references therein). The short-term climate changes play also an important role in marine areas near the mainland (Coffey & Read 2007;Caracciolo et al 2013;Zeller et al 2015).…”

“…The observed succession was deposited near to the land in an inner ramp lagoon and the related tidal flat environments where the siliciclastic input and coeval carbonate production were significantly controlled by different allocyclic (e.g., climatic or sea-level changes) factors (see also Brachert et al 2003;Colombié et al 2012;Chiarella et al 2017). The studied section of the Construction site was deposited between the Late Anisian and Carnian based on its stratigraphic position (Rálisch-Felgenhauer & Török 1993;Török 1998;Haas 2001) and vertebrate fossils (Ősi et al 2013), which period was frequently characterized by significant fluctuation in the climatic conditions and rainfall intensity (e.g., Mutti & Weissert 1995;Simms et al 1995;Feist-Burkhardt et al 2008;Preto et al 2010).…”

“…The bone-bearing successions of the Villány Hills were deposited in an inner ramp environment (Rálisch-Felgenhauer & Török 1993;Török 2000, and see below) representing the transition zone between the upper shoreface and fair-weather wave base (Burchette & Wright 1992). Mixed siliciclastic-carbonate deposits frequently accommodate in such environments consisting of both extrabasinal (e.g., terrigenous siliciclastic) and intrabasinal (autochthonous carbonate) components (Morsilli et al 2012;Caracciolo et al 2013;Chiarella et al 2017). The alternation of lithofacies and/or the sediment mixing can be interpreted as the result of short-term sea-level or short-term climate changes.…”

Granulometric and facies analysis of Middle–Upper Jurassic rocks of Ler Dome, Kachchh, western India: an attempt to reconstruct the depositional environment

“…17A), fossiliferous facies ( Fig. 17B), Dhosa Oolite facies embedded with lithoclastic-carbonates (Chiarella et al, 2017) (Fig. 17C) and matrix and clast-supported conglomerate facies (Fig.…”